[DSYenko]

Decking a block means the machine shop milled off a certain about of material to make the block level or flat so the cylinder head has a better seal.When the block is milled they are coincidentally taking material off the same surface that the original suffix codes /vin number is stamped into that matchs that block with the original vin of the body.When that is lost you actually can't say it "numbers matching" again.If they didnt mill an excessive amount off there are ways of being able to read the "lost" numbers/letters but thats another story in itself.